Perhaps all of us have watched at least a sci-fi movie that depicts a cloned version of an individual walking around and performing daily tasks (apart from trying to kill the original version), which makes us wonder when would cloning become an approachable reality. My answer: Not anytime soon.
So, what is Reproductive Cloning? Cloning involves the use of a process called Somatic Cell Nuclear Transfer (SCNT). In quick explanation, as part of a normal female’s oogenesis, the unfertilized oocytes are retrieved from donors at metaphase II during the meiosis process. Then, a small opening is created in the surrounding glycoprotein layer through which the DNA-containing components of the cell, the nucleus, and polar bodies are extracted and the somatic genomic materials of the cloning parent are delivered. The incorporation of a somatic diploid DNA is similar to the fertilization process, in which two haploid gametes fuse to create a new diploid DNA. Therefore, the oocytes would proceed to complete meiosis II, followed by mitotic division to create a blastocyst, which is then implanted in a female’s uterus (Kfoury, 2007).
However, the creation of a cloned embryo via SCNT involves many controversies and challenges that render the procedure unethical to practice on the egg donor, the pregnancy carrier, and the cloned children. Firstly, despite the recorded successes in forming cloned non-human offsprings, researchers have yet to fully comprehend SCNT's minuscule mechanism, evidenced by a limited efficiency rate that renders the technology unsafe to apply to a potential human. On average, only 1-5% of the created SCNT mammalian embryos fully developed and resulted in a live birth, half of which would pass away soon after due to various health complications, while the other half would live but suffer from impairments that significantly affect their life quality and expectancy, such as blindness, lacking limbs, digestion problems (CDC, 2019; National Academy Press, 2022).
Secondly, since SCNT has such a low success rate, there is a large need for donated eggs. The processes of hormonal stimulation and oocyte extractions can cause significant side effects, such as bruisings, discomforts, enlargement of ovaries, ovarian hyperstimulation syndrome, internal infections, hemorrhage, and organ damage; it also strongly correlates to long-term consequences of infertility and ovarian cancer in donors (Morris, 2016).
Moreover, since most of the implanted embryos have resulted in termination, the female beings carrying the embryos would also experience the detrimental consequences of pregnancy loss. Apart from the psychological impacts such as postpartum depression and grief, miscarriages, which happen at high occurrence for cloned blastocysts, have been closely associated with the development of chronic problems such as hypertension and diabetes (Okoth et al., 2022).
Therefore, given the lack of health benefits and potential risks to the children, donors, and embryo carriers, Human Reproductive SCNT goes against the core principle of "non-malfeasance" in medical science, the foundation upon which all biomedical research is built.
Figure 1. Illustration of the Somatic Cell Nuclear Transfer process (Mummery et al., 2014)
References
CDC. (2019). National Assisted Reproductive Technology Data-CDC. Centers for Disease Control and Prevention. Retrieved March 5, 2022, from https://nccd.cdc.gov/drh_art/rdPage.aspx?rdReport=DRH_ART.ClinicInfo&rdRequestForward=True&ClinicId=9999&ShowNational=1
Kfoury C. (2007). therapeutic cloning: promises and issues. McGill journal of medicine: MJM: an international forum for the advancement of medical sciences by students, 10(2), 112–120.
Morris, R. S. (2016). Complications and Side Effects of Oocyte Donation. In Principles of oocyte and embryo donation (pp. 97–107). essay, SPRINGER LONDON LTD.
Mummery, C. L., de, S. A. van, J., R. B. A., & Clevers, H. (2014). Chapter 6 - Cloning: History and Current Applications. In Stem cells: Scientific facts and fiction. essay, Elsevier/AP, Academic Press is an imprint of Elsevier.
National Academy Press. (2002). Appendix B: Animal reproductive cloning Data Tables on reproductive cloning Efficiency and Defects. In Scientific and medical aspects of human reproductive cloning (pp. 111–143). Essay.
Okoth, K., Subramanian, A., Chandan, J. S., Adderley, N. J., Thomas, G. N., Nirantharakumar, K., & Antza, C. (2022). Long-term miscarriage-related hypertension and diabetes mellitus. Evidence from a United Kingdom population-based cohort study. PLoS ONE, 17(1), e0261769. https://doi-org.dml.regis.edu/10.1371/journal.pone.0261769
Thu - thank you for your post! This was a super interesting topic. Cloning seems, to me, like a scientific advancement that is ridiculously futuristic. Like you said, it is portrayed in many sci-fi movies - and I think many people would accept that a reality like that seems so far out of reach. However, you have done a great job of breaking down the process of cloning and what it actually means at a cellular level. Now that I have read this before we have started our unit on reproduction in class, I will be interested to link the reproductive steps in cloning to the normal reproductive cycle.
ReplyDeleteOne idea that your post brought up for me is the idea of eugenics, and only reproducing desirable heritable characteristics in a human population. If cloning became an easily accessible reality, how could it go wrong? In other words, how could this technology in the wrong hands create mass populations with the exact desirable traits, whether those traits be good or bad. Both eugenics and scientific racism are ideas that are thrown around socially, but I read this interesting page from the NIH National Human Genome Research Institute basically debunking eugenics and scientific racism. The NIH says that eugenics is scientifically inaccurate and the genomics community is consistently working to "combat modern-day manifestations of eugenics and scientific racism, particularly as they affect people of color, people with disabilities and LGBTQ+ individuals" (NIH). Could cloning, compared to selective breeding, make those concepts closer to true? However, in my opinion, perfection is subjective, so we could never reach perfection. Your post leaves me with many questions, in the best possible way. Thank you for the great post!
Eugenics and scientific racism. Genome.gov. (n.d.). Retrieved October 16, 2022, from https://www.genome.gov/about-genomics/fact-sheets/Eugenics-and-Scientific-Racism.